Table 4.
Nutrient | Spearman correlation (r value) | Wilcoxon signed rank test (P value) | Percentage difference (%) | Cross-classification (Tertiles) | Weighted Kappa statistics (value) | Bland – Altman 2,3 Spearman Correlation (r value) | |
---|---|---|---|---|---|---|---|
Association (strength & direction) | Agreement | Agreement (size & direction of error) | Agreement (including chance) | Agreement (excluding chance) | Presence, direction and extent of bias | ||
% in same tertile | % in opposite tertile | ||||||
Level of validation | Individual | Group | Group | Individual | Individual | Individual | Group |
Energy (kJ) | 0.26 | P > 0.05 | −9.8 | 46.8 | 19.2 | 0.20 | P < 0.001 |
Validly interpretation | Acceptable | Good | Good | Poor | Poor | Acceptable | Biased |
Protein (g) | 0.23 | P < 0.01 | −19.1 | 42.6 | 23.4 | 0.12 | P < 0.05 |
Validly interpretation | Acceptable | Poor | Acceptable | Poor | Poor | Poor | Biased |
Fat (g) | 0.01 | P > 0.05 | −6.9 | 34.0 | 31.9 | −0.01 | P > 0.05 |
Validly interpretation | Poor | Good | Good | Poor | Poor | Poor | Not biased |
Carbohydrates (g) | 0.40 | P > 0.05 | −1.4 | 50.0 | 17.4 | 0.25 | P < 0.01 |
Validly interpretation | Acceptable | Good | Good | Good | Poor | Acceptable | Biased |
Folate (mcg) | 0.40 | P < 0.05 | 33.0 | 53.2 | 8.5 | 0.30 | P < 0.01 |
Validly interpretation | Acceptable | Poor | Poor | Good | Good | Acceptable | Biased |
Vitamin A (mcg) | 0.15 | P < 0.01 | −22.9 | 34.0 | 14.9 | 0.03 | P > 0.05 |
Validly interpretation | Poor | Poor | Poor | Poor | Poor | Poor | Not biased |
Iron (mg) | 0.38 | P > 0.05 | −24.8 | 51.1 | 23.4 | 0.29 | P < 0.01 |
Validly interpretation | Acceptable | Good | Poor | Good | Poor | Acceptable | Biased |
1Energy and nutrient intake derived from a QFFQ and four repeated 24-hour recalls conducted in 18–65 year old adults (n = 47, 11 males & 36 females) in a rural area in the Eastern Cape.
2% in LOA: Energy: 93.6%; protein: 95.7%, fat: 97.9%, carbohydrate: 95.7%; folate: 95.7%, vitamin A: 89.4%; iron: 98%.
3Upper & lower limits of agreement (LOA) and DRI for females aged 18 to 55: energy (kJ): −13406 & 10694 (EER: 10093 kJ); protein (g): −94.6 & 59.4 (RDA: 46 g); fat: −125.4 & 96.6 (no DRI); folate (mcg): −649 & 925.8 (RDA: 400mcg); vitamin A (mcg): −876 &576.4 (RDA: 700mcg); iron (mg): −22,4 &10.4 (RDA: ????mg).
Interpretation criteria for statistical tests.
Wilcoxon signed rank test: Good: p > 0.05; Poor: ≤ 0.05 [9].
Percentage difference: Good: 0.0 – 10.9%; Acceptable: 11.0 – 20.0%; Poor: > 20.0% [92].
Correlations coefficient (Spearman): Good: ≥ 0.50; Acceptable: 0.20 – 0.49; Poor < 0.20[2]
Cross-classification (Tertiles) (% in same tertile): Good: ≥ 50%; Poor: < 50% [2].
Cross-classification (% in opposite tertile): Good: ≤ 10%, Poor: > 10% [2].
Weighted Kappa statistics: Good: ≥ 0.61; Acceptable: 0.20 – 0.59; Poor: < 0.20 [2].
Bland-Altman - Correlation coefficient (Spearman): Good: P > 0.05; Poor: P ≤ 0.05 [2].